US4719092A - Reduction of nitrogen-based pollutants through the use of urea solutions containing oxygenated hydrocarbon solvents - Google Patents

Reduction of nitrogen-based pollutants through the use of urea solutions containing oxygenated hydrocarbon solvents Download PDF

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Publication number
US4719092A
US4719092A US06/784,828 US78482885A US4719092A US 4719092 A US4719092 A US 4719092A US 78482885 A US78482885 A US 78482885A US 4719092 A US4719092 A US 4719092A
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United States
Prior art keywords
effluent
urea
process according
solution
oxygenated hydrocarbon
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US06/784,828
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English (en)
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Wayne E. Bowers
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Fuel Tech Inc
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Fuel Tech Inc
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Application filed by Fuel Tech Inc filed Critical Fuel Tech Inc
Priority to US06/784,828 priority Critical patent/US4719092A/en
Assigned to FUEL TECH, INC., 61 TAYLOR REED PLACE, STAMFORD, CT. 06906, A CORP. OF MA. reassignment FUEL TECH, INC., 61 TAYLOR REED PLACE, STAMFORD, CT. 06906, A CORP. OF MA. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: BOWERS, WAYNE E.
Priority to DE198686906556T priority patent/DE242394T1/de
Priority to DE8686906556T priority patent/DE3687656T2/de
Priority to AT86906556T priority patent/ATE85032T1/de
Priority to JP61505543A priority patent/JPH07100131B2/ja
Priority to AU65249/86A priority patent/AU592386B2/en
Priority to EP86906556A priority patent/EP0242394B1/fr
Priority to PCT/US1986/002098 priority patent/WO1987002024A1/fr
Priority to CA000519895A priority patent/CA1255475A/fr
Priority to US07/108,779 priority patent/US4844878A/en
Publication of US4719092A publication Critical patent/US4719092A/en
Application granted granted Critical
Priority to DD88320784A priority patent/DD275620A5/de
Assigned to FUEL TECH, INC. reassignment FUEL TECH, INC. SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: NALCO FUEL TECH, INC.
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/54—Nitrogen compounds
    • B01D53/56—Nitrogen oxides

Definitions

  • the present invention relates to improvements in the combustion of carbonaceous fuels, and more particularly to improvements in firing large boilers with reduced emissions of nitrogen-based pollutants.
  • Carbonaceous fuels burn more completely, with reduced emissions of carbon monoxide and unburned hydrocarbons, at oxygen concentrations and combustion air/fuel ratios which permit optimized high flame temperatures.
  • these temperatures are above 2000° F. and typically from about 2200° F. to 3000° F.
  • these high temperatures and hot spots of higher temperature tend to result in the production of thermal NO x --the temperatures being so high that free radicals of nitrogen and oxygen are formed and chemically combine as nitrogen oxides (NO x ).
  • the flame temperature can be lowered to reduce NO x formation by the use of large excesses air or fuel, or a hybrid of both processes known as staged combustion.
  • staged combustion a hybrid of both processes known as staged combustion.
  • these approaches create excessive carbon-based pollutants.
  • Lyon discloses a non-catalytic system for reducing nitrogen monoxide (NO) in a combustion effluent.
  • Lyon discloses that ammonia and specified ammonia precursors or their aqueous solutions, can be injected into the effluent for mixing with the nitrogen monoxide at a temperature within the range of 1600° F. to 2000° F.
  • a reducing agent can be mixed with the effluent to permit the reduction reaction to occur at temperatures as low as 1300° F., thereby assuring avoidance of high temperature oxidation of ammonia to nitrogen monoxide.
  • Lyon discloses that hydrogen is preferred as compared to aromatic, parafinic and olefinic hydrocarbons and oxygenated hydrocarbons, and discloses nothing with regard to the control of ammonia in the final effluent.
  • Williamson discloses the purification of acid gas-containing streams at low temperatures approaching ambient. Williamson discloses contacting the gas stream with an amine vapor in sufficient concentration such that its partial pressure is at least 5% of the total pressure of the gas stream. This system thus requires large amounts of the treating gas and does not address the issue of ammonia gas in the final effluent.
  • Arand et al disclose the non-catalytic urea reduction of nitrogen oxides in fuel-rich combustion effluents. They indicate that under fuel-rich conditions, aqueous solutions of urea at concentrations of greater than 10%, and preferably greater than 20%, are effective nitrogen oxide reducers at temperatures in excess of 1900° F. This is the effluent from staged combustion which results in the production of high levels of carbonaceous pollutants.
  • the present invention provides a process for reducing the concentration of nitrogen oxides in an oxygen-rich effluent from the combustion of a carbonaceous fuel while maintaining low levels of ammonia therein.
  • the process comprises injecting an aqueous solution of urea and an oxygenated hydrocarbon into said effluent at an effluent temperature above 1600° F.
  • a preferred embodiment of the invention provides for introducing a dilute aqueous solution of the urea and the oxygenated hydrocarbon at a plurality of injection points utilizing droplets having a Sauter mean diameter within the range of from about 50 to about 10,000 microns to achieve uniform mixing of the urea and the oxygenated hydrocarbon with the effluent gas.
  • the effluents can be at temperatures in excess of 2000° F.
  • urea and other compounds equivalent in effect.
  • the compounds are ammonium carbonate, ammonium formate, ammonium oxalate, ammonium hydroxide and various stable amines including hexamethylenetetramine, and mixtures of these.
  • reference in this disclosure to urea should not be taken as limiting to urea itself but should extend to urea and all of its equivalents.
  • the term equivalent is not limited to exact equivalents, and various materials within the listing of equivalents will be optimally operable at some conditions which are different than those for other of the listed materials. Moreover, some of the materials may be more effective than others.
  • the urea is preferably supplied to the effluent as an aqueous solution, and its concentration in the solution will be at least effective to reduce the level of NO x in the effluent.
  • the solution can be varied from saturated to very dilute. At higher effluent temperatures, the concentration of urea will be more dilute, say less than 20% at 2000° F., and from 0.5% to 10% at these or higher temperatures. On the other hand, concentrations of from 20% to 40% are more typical for temperatures below 2000° F.
  • the concentration of the urea within the effluent gas should be sufficient to provide a reduction in nitrogen oxide levels.
  • the urea will be employed at a molar ratio of urea to the baseline nitrogen oxide level of from about 1 to 4 to about 5 to 1, and will more preferably be within the range of from about 2 to 1 to about 1 to 2.
  • oxygenated solvents are low molecular weight ketones, aldehydes and mono, di or polyhydric alcohols of aliphatic hydrocarbons having one to four carbons.
  • Ethylene glycol is a preferred oxygenated hydrocarbon for this purpose.
  • Mixtures of polyols, such as those mixtures of low molecular weight polyols known as hydrogenated starch hydrolysates, can also be employed.
  • the level of oxygenated hydrocarbon solvent employed should, at a minimum, be an amount effective to reduce the level of free ammonia in the effluent, and can be employed as a total replacement for water.
  • the oxygenated hydrocarbon will be employed at a level of at least about 10% by weight of the urea in solution.
  • Weight ratios of ethylene glycol to urea will be within the range of from about 1:4 to 4:1, and preferably closer to unity, e.g., 1:2 to 2:1. These weight ratios apply to other oxygenated solvents as well, which can be employed in combination if desired.
  • the urea solution will often, of necessity, be dispersed within the effluent gas stream at a point where the effluent is at a temperature above 2000° F.
  • Large industrial boilers of the type employed for utility power plants and other large facilities will typically be water jacketted and have access only at limited points. In the most typical situation, the boiler interior can be accessed only through burner access ports and at access ports above the flame, where the temperatures at full load are typically within the range of from about 2050° F. to about 2600° F.
  • the temperature at this point of access will typically fall within the range of from about 2100° F. to about 2600° F., and when fired with coal or oil, will typically fall within the range of about 2050° F. to 2400° F. These temperatures will not permit the effective introduction of solid urea or urea solutions as previously disclosed to the art.
  • the urea solutions according to the present invention are preferably injected at a number of spaced points where there is sufficient turbulence to distribute the droplets throughout the effluent.
  • the solutions are injected from nozzles which are effective to uniformly form and disperse droplets of the solutions within the flowing effluent stream.
  • the nozzles are located at a sufficient number of points to achieve uniform mixing.
  • the size of the droplets of solution will be within the range of from about 10 to about 10,000, and preferably be greater than about 50 microns.
  • the droplet size is important to enable uniform mixing of the urea with the effluent and penetration of the urea sufficiently along the internal boiler path that it can achieve its intended function.
  • the size of the droplets will preferably be increased with increasing temperature. At temperatures below 200° F., droplet sizes of less than 150 microns are quite effective, while at higher temperatures the droplets should be larger, and preferably larger than 500 microns.
  • the following example describes the reduction of nitrogen oxide with control of ammonia levels in the effluent from a commercial utility boiler system.
  • test runs and the data recorded therefrom are set forth in the following table.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • General Chemical & Material Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Biomedical Technology (AREA)
  • Analytical Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Treating Waste Gases (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
  • Solid Fuels And Fuel-Associated Substances (AREA)
US06/784,828 1985-10-04 1985-10-04 Reduction of nitrogen-based pollutants through the use of urea solutions containing oxygenated hydrocarbon solvents Expired - Lifetime US4719092A (en)

Priority Applications (11)

Application Number Priority Date Filing Date Title
US06/784,828 US4719092A (en) 1985-10-04 1985-10-04 Reduction of nitrogen-based pollutants through the use of urea solutions containing oxygenated hydrocarbon solvents
DE8686906556T DE3687656T2 (de) 1985-10-04 1986-10-03 Ermaessigung stickstoffhaltiger schadstoffe durch verwendung von sauerstoffhaltiges kohlenwasserstoffloesungsmittel aufweisendem harnstoffloesungen.
AU65249/86A AU592386B2 (en) 1985-10-04 1986-10-03 Reduction of nitrogen-based pollutants through the use of urea solutions containing oxygenated hydrocarbon solvents
PCT/US1986/002098 WO1987002024A1 (fr) 1985-10-04 1986-10-03 Diminution des polluants a base d'azote par l'emploi de solution d'uree contenant des solvants d'hydrocarbure oxygene
AT86906556T ATE85032T1 (de) 1985-10-04 1986-10-03 Ermaessigung stickstoffhaltiger schadstoffe durch verwendung von sauerstoffhaltiges kohlenwasserstoffloesungsmittel aufweisendem harnstoffloesungen.
JP61505543A JPH07100131B2 (ja) 1985-10-04 1986-10-03 酸素含有炭化水素溶媒を含む尿素溶液を使用する，窒素ベ−スの汚染物質の削減
DE198686906556T DE242394T1 (de) 1985-10-04 1986-10-03 Ermaessigung stickstoffhaltiger schadstoffe durch verwendung von sauerstoffhaltiges kohlenwasserstoffloesungsmittel aufweisendem harnstoffloesungen.
EP86906556A EP0242394B1 (fr) 1985-10-04 1986-10-03 Diminution des polluants a base d'azote par l'emploi de solution d'uree contenant des solvants d'hydrocarbure oxygene
CA000519895A CA1255475A (fr) 1985-10-04 1986-10-06 Reduction des polluants azotes par l'utilisation de solutions d'uree contenant des solvants d'hydrocarbure oxygene
US07/108,779 US4844878A (en) 1985-10-04 1987-10-14 Process for the reduction of nitrogen oxides in an effluent
DD88320784A DD275620A5 (de) 1985-10-04 1988-10-14 Verfahren zur verringerung der konzentration an stickoxiden in einem abstrom

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US06/784,828 US4719092A (en) 1985-10-04 1985-10-04 Reduction of nitrogen-based pollutants through the use of urea solutions containing oxygenated hydrocarbon solvents

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US07/108,779 Continuation-In-Part US4844878A (en) 1985-10-04 1987-10-14 Process for the reduction of nitrogen oxides in an effluent

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US (1) US4719092A (fr)
EP (1) EP0242394B1 (fr)
JP (1) JPH07100131B2 (fr)
AT (1) ATE85032T1 (fr)
AU (1) AU592386B2 (fr)
CA (1) CA1255475A (fr)
DD (1) DD275620A5 (fr)
DE (2) DE3687656T2 (fr)
WO (1) WO1987002024A1 (fr)

Cited By (40)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4851201A (en) * 1987-04-16 1989-07-25 Energy And Environmental Research Corporation Methods of removing NOx and SOx emissions from combustion systems using nitrogenous compounds
EP0326943A2 (fr) * 1988-02-02 1989-08-09 KRC Umwelttechnik GmbH Procédé et dispositif pour la réduction d'oxydes d'azote utilisant une injection de chaudière à deux étages
WO1989007982A1 (fr) * 1988-02-26 1989-09-08 Fuel Tech, Inc. Procede et injecteur reduisant la concentration de polluants dans un effluent
US4927612A (en) * 1985-10-04 1990-05-22 Fuel Tech, Inc. Reduction of nitrogen- and carbon-based pollutants
US4978514A (en) * 1989-09-12 1990-12-18 Fuel Tech, Inc. Combined catalytic/non-catalytic process for nitrogen oxides reduction
US4985218A (en) * 1989-03-03 1991-01-15 Fuel Tech, Inc. Process and injector for reducing the concentration of pollutants in an effluent
US4997631A (en) * 1990-03-07 1991-03-05 Fuel Tech, Inc. Process for reducing nitrogen oxides without generating nitrous oxide
US5048432A (en) * 1990-12-27 1991-09-17 Nalco Fuel Tech Process and apparatus for the thermal decomposition of nitrous oxide
US5078982A (en) * 1990-09-20 1992-01-07 Molecular Technology Corporation Reduction of nitrogen oxide in effluent gases using formaldehyde
US5087431A (en) * 1990-09-20 1992-02-11 Molecular Technology Corporation Catalytic decomposition of cyanuric acid and use of product to reduce nitrogen oxide emissions
US5171554A (en) * 1990-09-20 1992-12-15 Molecular Technology Corporation Conversion of formaldehyde and nitrogen to a gaseous product and use of gaseous product in reduction of nitrogen oxide in effluent gases
US5171558A (en) * 1990-09-20 1992-12-15 Molecular Technology Corporation Catalytic decomposition of cyanuric acid and use of product to reduce nitrogen oxide emissions
US5192515A (en) * 1990-09-20 1993-03-09 Molecular Technology Corporation Reduction of nitrogen oxide and carbon monoxide in effluent gases
US5229090A (en) * 1991-07-03 1993-07-20 Nalco Fuel Tech Process for nitrogen oxides reduction to lowest achievable level
US5234670A (en) * 1990-09-20 1993-08-10 Molecular Technology Corporation Reduction of nitrogen oxide in effluent gases using NCO radicals
US5234671A (en) * 1990-09-20 1993-08-10 Molecular Technology Corporation Reduction of nitrogen oxide in effluent gases using formaldehyde and/or formaldehyde-derived free radicals
US5240689A (en) * 1989-06-19 1993-08-31 Noell, Inc. Process using two-stage boiler injection for reduction of nitrogen
US5262138A (en) * 1989-08-31 1993-11-16 Union Oil Company Of California Process for NOx abatement
WO1994008895A1 (fr) * 1992-10-13 1994-04-28 Nalco Fuel Tech Procede et composition destines a reduire la pollution
WO1994008893A1 (fr) * 1992-10-13 1994-04-28 Nalco Fuel Tech Procede et composition destines a la lutte contre la pollution
US5342599A (en) * 1990-09-14 1994-08-30 Cummins Power Generation, Inc. Surface stabilized sources of isocyanic acid
US5342592A (en) * 1989-07-04 1994-08-30 Fuel Tech Europe Ltd. Lance-type injection apparatus for introducing chemical agents into flue gases
WO1994026659A1 (fr) * 1993-05-07 1994-11-24 Nalco Fuel Tech PROCEDE ET APPAREIL POUR AMELIORER LA REPARTITION DE PRODUITS CHIMIQUES REDUISANT LE NOx DANS UN ENVIRONNEMENT A HAUTE TENEUR EN MATIERES SOLIDES
US5404841A (en) * 1993-08-30 1995-04-11 Valentine; James M. Reduction of nitrogen oxides emissions from diesel engines
US5462718A (en) * 1994-06-13 1995-10-31 Foster Wheeler Energy Corporation System for decreasing NOx emissions from a fluidized bed reactor
US5478542A (en) * 1992-11-23 1995-12-26 Nalco Fuel Tech Process for minimizing pollutant concentrations in combustion gases
US5543123A (en) * 1990-08-01 1996-08-06 Nalco Fuel Tech Low pressure formation of a urea hydrolysate for nitrogen oxides reduction
US5658547A (en) * 1994-06-30 1997-08-19 Nalco Fuel Tech Simplified efficient process for reducing NOx, SOx, and particulates
US5681536A (en) * 1996-05-07 1997-10-28 Nebraska Public Power District Injection lance for uniformly injecting anhydrous ammonia and air into a boiler cavity
US5728357A (en) * 1996-04-10 1998-03-17 Nalco Fuel Tech Reduction of NOx emissions from rotary cement kilns by selective noncatalytic reduction
US5985222A (en) * 1996-11-01 1999-11-16 Noxtech, Inc. Apparatus and method for reducing NOx from exhaust gases produced by industrial processes
US6001152A (en) * 1997-05-29 1999-12-14 Sinha; Rabindra K. Flue gas conditioning for the removal of particulates, hazardous substances, NOx, and SOx
US6258336B1 (en) 1995-06-09 2001-07-10 Gas Research Institute Method and apparatus for NOx reduction in flue gases
US6280695B1 (en) 2000-07-10 2001-08-28 Ge Energy & Environmental Research Corp. Method of reducing NOx in a combustion flue gas
US6436359B1 (en) 2000-10-25 2002-08-20 Ec&C Technologies, Inc. Method for controlling the production of ammonia from urea for NOx scrubbing
US20030109047A1 (en) * 2001-11-09 2003-06-12 Valentine James M. Continuously-variable control of pollution reducing chemicals for combustion sources
US20080291965A1 (en) * 2007-05-18 2008-11-27 Environmental Energy Services, Inc. Method for measuring ash/slag deposition in a utility boiler
US20090148370A1 (en) * 2007-12-06 2009-06-11 Spencer Iii Herbert W Process to produce ammonia from urea
US9586831B2 (en) 2014-06-09 2017-03-07 Wahlco, Inc. Urea to ammonia process
US11027237B2 (en) 2019-07-19 2021-06-08 American Electric Power Company, Inc. Direct injection of aqueous urea

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US4844878A (en) * 1985-10-04 1989-07-04 Fuel Tech, Inc. Process for the reduction of nitrogen oxides in an effluent
AU585670B2 (en) * 1985-10-04 1989-06-22 Fuel Tech. Inc. Reduction of nitrogen- and carbon-based pollutants through the use of urea solutions
US4830839A (en) * 1987-02-13 1989-05-16 Fuel Tech, Inc. Ammonia scrubbing
US5192338A (en) * 1987-09-03 1993-03-09 Commonwealth Scientific And Industrial Research Organisation Coal ash modification and reduction
ZA886518B (en) * 1987-09-03 1989-05-30 Commw Scient Ind Res Org Coal ash modification and reduction
AT390208B (de) * 1988-05-09 1990-04-10 Waagner Biro Ag Verfahren zur entfernung von stickoxiden
US5457223A (en) * 1992-10-09 1995-10-10 The Standard Oil Company Process for elimination of waste material during manufacture of acrylonitrile
CA2141734C (fr) * 1995-01-25 2000-06-06 Raj Narain Pandey Reduction catalytique selective d'oxydes d'azote
DE10021517C1 (de) * 2000-05-03 2002-01-10 Kuelps Heinz Juergen Zurückdrängung und Verminderung der Hochtemperatur-Halogen-Korrosion in Verbrennungsanlagen durch den Einsatz von Wirkstoffen sowie Wirkstoff-Mischungen
EP2138766B1 (fr) * 2008-06-23 2016-03-30 Hitachi Zosen Inova AG Procédé destiné à l'injection d'une matière dans une cuvette d'une installation d'incinération des déchets
FR2941869B1 (fr) * 2009-02-10 2013-03-29 Novergie Procede de reduction des oxydes d'azote issus de la combustion des combustibles solides
JP5812630B2 (ja) * 2011-03-02 2015-11-17 三菱重工環境・化学エンジニアリング株式会社 廃棄物焼却プラント
CN102721797B (zh) * 2011-09-22 2014-11-05 辽宁省电力有限公司 无烟煤在热解中生成HCN/NH3与在锅炉中燃烧生成NOx的关联性的分析方法
KR102104050B1 (ko) * 2019-05-21 2020-04-24 오미혜 질소산화물 저감용 조성물 및 질소산화물을 저감시키는 방법

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Cited By (51)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4927612A (en) * 1985-10-04 1990-05-22 Fuel Tech, Inc. Reduction of nitrogen- and carbon-based pollutants
US4851201A (en) * 1987-04-16 1989-07-25 Energy And Environmental Research Corporation Methods of removing NOx and SOx emissions from combustion systems using nitrogenous compounds
EP0326943A2 (fr) * 1988-02-02 1989-08-09 KRC Umwelttechnik GmbH Procédé et dispositif pour la réduction d'oxydes d'azote utilisant une injection de chaudière à deux étages
EP0326943A3 (fr) * 1988-02-02 1990-05-16 KRC Umwelttechnik GmbH Procédé et dispositif pour la réduction d'oxydes d'azote utilisant une injection de chaudière à deux étages
WO1989007982A1 (fr) * 1988-02-26 1989-09-08 Fuel Tech, Inc. Procede et injecteur reduisant la concentration de polluants dans un effluent
US4985218A (en) * 1989-03-03 1991-01-15 Fuel Tech, Inc. Process and injector for reducing the concentration of pollutants in an effluent
US5240689A (en) * 1989-06-19 1993-08-31 Noell, Inc. Process using two-stage boiler injection for reduction of nitrogen
US5342592A (en) * 1989-07-04 1994-08-30 Fuel Tech Europe Ltd. Lance-type injection apparatus for introducing chemical agents into flue gases
US5399326A (en) * 1989-08-31 1995-03-21 Union Oil Company Of California Process for noncatalytic NOx abatement
US5262138A (en) * 1989-08-31 1993-11-16 Union Oil Company Of California Process for NOx abatement
WO1991004224A1 (fr) * 1989-09-12 1991-04-04 Fuel Tech, Inc. Procede combine catalytique/non catalytique de reduction des oxydes azotes
US4978514A (en) * 1989-09-12 1990-12-18 Fuel Tech, Inc. Combined catalytic/non-catalytic process for nitrogen oxides reduction
US4997631A (en) * 1990-03-07 1991-03-05 Fuel Tech, Inc. Process for reducing nitrogen oxides without generating nitrous oxide
US5543123A (en) * 1990-08-01 1996-08-06 Nalco Fuel Tech Low pressure formation of a urea hydrolysate for nitrogen oxides reduction
US5342599A (en) * 1990-09-14 1994-08-30 Cummins Power Generation, Inc. Surface stabilized sources of isocyanic acid
US5171554A (en) * 1990-09-20 1992-12-15 Molecular Technology Corporation Conversion of formaldehyde and nitrogen to a gaseous product and use of gaseous product in reduction of nitrogen oxide in effluent gases
US5234670A (en) * 1990-09-20 1993-08-10 Molecular Technology Corporation Reduction of nitrogen oxide in effluent gases using NCO radicals
US5234671A (en) * 1990-09-20 1993-08-10 Molecular Technology Corporation Reduction of nitrogen oxide in effluent gases using formaldehyde and/or formaldehyde-derived free radicals
US5192515A (en) * 1990-09-20 1993-03-09 Molecular Technology Corporation Reduction of nitrogen oxide and carbon monoxide in effluent gases
US5171558A (en) * 1990-09-20 1992-12-15 Molecular Technology Corporation Catalytic decomposition of cyanuric acid and use of product to reduce nitrogen oxide emissions
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CA1255475A (fr) 1989-06-13
AU6524986A (en) 1987-04-24
EP0242394B1 (fr) 1993-01-27
EP0242394A4 (fr) 1988-10-27
DE3687656D1 (de) 1993-03-11
EP0242394A1 (fr) 1987-10-28
ATE85032T1 (de) 1993-02-15
DE242394T1 (de) 1988-02-25
DD275620A5 (de) 1990-01-31
JPH07100131B2 (ja) 1995-11-01
WO1987002024A1 (fr) 1987-04-09
DE3687656T2 (de) 1993-05-19
JPS63502087A (ja) 1988-08-18
AU592386B2 (en) 1990-01-11

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